# rxGate

x-axis rotation gate

Since R2023a

Installation Required: This functionality requires MATLAB Support Package for Quantum Computing.

## Syntax

``g = rxGate(targetQubit,theta)``

## Description

example

````g = rxGate(targetQubit,theta)` applies an x-axis rotation gate to a single target qubit and returns a `quantum.gate.SimpleGate` object. This gate rotates the qubit state around the x-axis by an angle of `theta`. If `targetQubit` and `theta` are vectors of the same length, `rxGate` returns a column vector of gates, where `g(i)` represents an x-axis rotation gate applied to a qubit with index `targetQubit(i)` with a rotation angle of `theta(i)`. If either `targetQubit` or `theta` is a scalar, and the other input is a vector, then MATLAB® expands the scalar to match the size of the vector input.```

## Examples

collapse all

Create an x-axis rotation gate that acts on a single qubit with rotation angle `pi/2`.

`g = rxGate(1,pi/2)`
```g = SimpleGate with properties: Type: "rx" ControlQubits: [1×0 double] TargetQubits: 1 Angles: 1.5708```

Get the matrix representation of the gate.

`M = getMatrix(g)`
```M = 0.7071 + 0.0000i 0.0000 - 0.7071i 0.0000 - 0.7071i 0.7071 + 0.0000i```

Create an array of three x-axis rotation gates. The first gate acts on qubit 1 with rotation angle `pi/4`, the next gate acts on qubit 2 with rotation angle `pi/2`, and the final gate acts on qubit 3 with rotation angle `3*pi/4`.

`g = rxGate(1:3,pi/4*(1:3))`
```g = 3×1 SimpleGate array with gates: Id Gate Control Target Angle 1 rx 1 pi/4 2 rx 2 pi/2 3 rx 3 3pi/4```

## Input Arguments

collapse all

Target qubit of the gate, specified as a positive integer scalar index or vector of qubit indices.

Example: `1`

Example: `3:5`

Rotation angle, specified as a real scalar or vector.

Example: `pi`

Example: `(1:3)*pi/2`

collapse all

### Matrix Representation of x-Axis Rotation Gate

The matrix representation of an x-axis rotation gate applied to a target qubit with a rotation angle of $\theta$ is

`$\left[\begin{array}{cc}\mathrm{cos}\left(\frac{\theta }{2}\right)& -i\mathrm{sin}\left(\frac{\theta }{2}\right)\\ -i\mathrm{sin}\left(\frac{\theta }{2}\right)& \mathrm{cos}\left(\frac{\theta }{2}\right)\end{array}\right].$`

Applying this gate with rotation angle $\theta =\pi$ is equivalent to applying a Pauli X gate (`xGate`) up to a global phase factor.

## Version History

Introduced in R2023a